BUOYANCY ASSESSED WITH FLOATING TESTS AND UNDERWATER WEIGHING. A PILOT STUDY

Abstract

The aim of the present study was to compare the buoyancy assessed by floating tests with the buoyancy calculated using the variables measured during underwater weighing. We also aimed to evaluate the relationship between assessed buoyancy and body composition. Twenty-seven women (age: 20 ± 3 years, height: 1.66 ± 0.34 m, weight: 62 ± 7 kg; body mass index: 22 ± 2; vital capacity: 4.26 ± 0.47 l) and twenty-six men (age: 19 ± 2 years, height: 1.81 ± 6.76 m, weight: 79 ± 10 kg body mass index: 24 ± 3; vital capacity: 6.05 ± 0.7 l) volunteered to participate in the study. They performed floating tests, underwater weighing, pulmonary function measurement, and body composition procedure on the same day in random order with a 30-minute break. Floating testing consisted of one horizontal (HT) and two vertical tests with different arm positions, i.e., arms adducted to the body (VT1) or arms extended overhead (VT2). We assessed participants' buoyancy (B-HT, B-VT1, and B-VT2). In addition, we calculated participants' body volume and buoyancy (B-c) using variables measured during underwater weighing. Results showed that B-c was moderately correlated with B-VT1 (Spearman's ρ = 0.51; p < 0.001) and B-VT2 (Spearman's ρ = 0.55; p < 0.001), but not with B-HT. Multiple regression analysis showed that vital capacity and muscle mass had a positive and negative effect, respectively, on the scores of buoyancy assessed by vertical floating tests. In addition, the mass of the arms correlated negatively with the scores of buoyancy assessed by VT2 (β = -6.26; p = 0.005). According to the obtained results, we can conclude that both vertical floating tests i.e. with arms adducted to the body or arms extended overhead are suitable substitutes for underwater weighing to determine buoyancy, which is strongly related to vital capacity and lesser extent to muscle mass. Muscle mass is not a factor that can be changed immediately, while the amount of inspiration can be regulated. Therefore, the control of breathing and thus the reduction or increase of buoyancy is an important skill that novice swimmers should acquire as part of the learn-to-swim program.